自动生成四则运算题目

 1 #include<stdio.h>
 2 #include<Windows.h>
 3 #include<time.h>
 4 void main()
 5 {
 6     int a, b, c, d,i,m,n;
 7     float p, q;
 8     srand(unsigned( time(NULL)));//这个函数调用中使用（time（NULL））；这个函数调用中使用time（NULL）函数返回值（当前时间）作实参。初始化随机数发生器。
 9     for (i = 0; i < 30; i++)
10     {
11         a = rand() % 100;//rand（）返回一个随机数，但是每次调用时，随机数发生器返回的随机数序列都是一样的，所以，用当前时间（time（NULL））返回值作为种子对随机数发生器进行初始化，由于每次当前时间不一样，所以随机数发生器产生的随机数序列不一样，即rand（）函数调用的返回值不一样，就达到了得真随机数而不是伪随机数的目的。
12         b = rand() % 100;
13         c = rand() % 5;
14         switch (c)
15         {
16         case 0: printf("%d + %d =\n", a, b);
17             break;
18         case 1:if (a < b)
19         {
20                    d = a;
21                    a = b;
22                    b = d;
23         }
24                printf("%d - %d =\n", a, b);
25                break;
26         case 2:printf("%d * %d =\n", a, b);
27             break;
28         case 3:
29             while (b == 0)
30             {
31                 b = rand() % 100;
32             }
33             printf("%d / %d =\n", a, b);
34             break;
35         case 4:
36             a = rand() % 100;
37             b = rand() % 100;
38             m = rand() % 100;
39             n = rand() % 100;
40             c = rand() %4 ;
41             while (b == 0)
42             {
43                 b = rand() % 100;
44             }
45             while (n == 0)
46             {
47                 n = rand() % 100;
48             }
49             if (a > b)
50             {
51                 d = a;
52                 a = b;
53                 b = d;
54             }
55             if (m > n)
56             {
57                 d = m;
58                 m = n;
59                 n = d;
60             }
61             switch (c)
62             {
63             case 0:printf("%d/%d + %d/%d =\n", a, b, m, n);
64                 break;
65             case 1:
66                 p = (float)a / (float)b;
67                 q = (float)m / (float)n;
68                 if (p < q)
69                 {
70                     d = a;
71                     a = m;
72                     m = d;
73                     d = b;
74                     b = n;
75                     n = d;
76                 }
77                 printf("%d/%d - %d/%d =\n", a,b,m,n);
78                 break;
79             case 2:printf("%d/%d * %d/%d =\n", a, b, m, n);
80                 break;
81             case 3:
82                 a = rand() % 100;
83                 b = rand() % 100;
84                 m = rand() % 100;
85                 n = rand() % 100;
86                 c = rand() % 4;
87                 while (m == 0)
88                 {
89                     m = rand() % 100;
90                 }
91                 printf("%d/%d / %d/%d =\n", a, b, m, n);
92                 break;
93             }
94         }
95     }
96     system("pause");
97 }